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Stars’ escape velocity shows how to exit the Milky Way

By Anil Ananthaswamy

GETTING out of the galaxy might take an antimatter engine. Future explorers fleeing the Milky Way will have to boost their spaceship to 0.2 per cent of the speed of light, according to a study of fast-moving stars in our galaxy.

Joss Bland-Hawthorn at the University of Sydney, Australia, and colleagues used data from the Radial Velocity Experiment survey, which measured the distances and speeds of 426,000 stars. The team used these findings and other data to select 90 high-velocity stars whose speeds and positions had been determined most precisely, and used them to estimate the mass of the Milky Way at about 1.6 trillion suns.

With the mass of the galaxy in hand, the team calculated the escape velocity for objects in the vicinity of our solar system. To escape the gravitational clutches of our galaxy, a spaceship would need to hit 537 kilometres per second (arxiv.org/abs/1309.4293). For context, a rocket needs to roar off at just 11.2 kilometres per second to escape Earth’s gravity.

Conventional rocket engines would take too much fuel, but Bland-Hawthorn speculates that the energy released by annihilating matter with antimatter could do the trick. “I know it’s a crazy idea,” he says.